Latest ArticlesA ternary complex combining dual-phase perovskites - Cs4PbBr6/CsPbBr3 (DP-CPB) with ZnSe micropsheres (ZnSe-DP-CPB) was successfully prepared using supersaturated recrystallization technique at room temperature. It was showed that the DP-CPB composites were partially embedded in ZnSe microsphere composed with ZnSe NCs. The light absorption range of ZnSe-DP-CPB composites was extended from visible to near infrared light. Highly enhanced luminescence from ZnSe-DP-CPB composite was observed and the excitation power-dependent photoluminescence showed that the recombination involves excitons. The recombination lifetimes of the ternary composites increased compared with DP-CPB composite, indicating that the non-radiative combination was suppressed which may be possibly due to the decrease of both bulk and surface defects, owing to the passivation of ZnSe, as well as the suitable band alignments of these three components. The ternary complex also showed improved stability of photoluminescence (PL), which opens a new avenue for enhancing the stability of PL and optoelectronic applications for semiconductor-perovskite composites.
An iron (Ⅲ) cluster, namely [Fe10(μ3-O)8L8(NO3)6] (1), has been synthesized by treatment of Fe (NO3)3·9H2O with 3, 5-dimethyl-1-(hydroxymethyl)-pyrazole (HL) under ambient temperature. The core skeleton of {FeⅢ10} can be regarded as a pear-like cage with eight triangular {FeⅢ3(μ3-O)} units, in which each three FeⅢ centers is held together by one μ3-O2- group with FeⅢ centers as corner-sharing triangle units. Importantly, {FeⅢ10} cluster is not only stable in solid state but also in solution, which is confirmed by powder X-ray diffraction (PXRD) pattern and electrospray ionization mass spectrometry (ESI-MS), respectively. Furthermore, 1 shows antiferromagnetic exchange behavior arising from the interactions between the iron(Ⅲ) centers.
The realization of good aqueous dispersibility of commercial graphene products composed of exfoliated graphene sheets is of significance for downstream applications. However, the tap density of commercial graphene powder is quite low (0.03-0.1 kg/m3), meaning that 1 kg graphene powder occupies about 10-30 m3 in volume during transportation. And, the available content of commercial graphene dispersion/slurry in aqueous medium cannot exceed 5 wt%, although the density is high (≈1050 kg/m3). In this work, a graphene monolith was prepared by oven-drying of graphene sheets prefunctionalized with poloxamer surfactants. Our graphene monoliths not only have a high density (1500 kg/m3) and high graphene content (≈10 wt%), but also a full capability to be completely redispersed (≈100%) in water by bath sonication to obtain solubilized graphene sheets, whose lateral size and thickness are unchanged compared to as-exfoliated ones. Moreover, a simple empirical method was proposed to predict the redispersion capability of graphene monoliths using different poloxamers by contact angle measurements. Our results provide a universal approach to make exfoliated graphene-based products with better downstream availability and lower transportation cost.
Ru and Co are highly dispersed on the surface of TiO2 nanoparticles with an easy coprecipitation method to fabricate a novel Ru-based catalyst (Ru/Co-TiO2). The fabricated Ru/Co-TiO2 catalyst exhibits superior catalytic performance for promoting NaBH4 hydrolysis in alkaline medium, showing an impressive hydrogen generation rate per gram Ru as high as 172 L min-1 gRu-1, which is better than most of recently reported Ru-based catalysts. In addition, the fabricated Ru/Co-TiO2 catalyst also shows excellent durability in cycle use, with only 2.9% activity loss after being used for 5 cycles.These advantages make the developed Ru/ Co-TiO2 catalyst a potential choice for promoting hydrogen generation from NaBH4 hydrolysis.
Pathogen infection is the main cause of human morbidity and death. Traditional antibiotics usually sterilize bacteria in chemical ways, which tends to develop serious antibiotic resistance. Cationic polymers exhibit good bacterial inhibition with less resistance, but often face severe cytotoxicity toward normal cells. The optimization of polymeric antimicrobials for enhanced bactericidal capacity and improved biocompatibility is quite meaningful. In addition, photodynamic therapy (PDT) is a therapeutic modality with less susceptibility to develop resistance. Herein, a typical commercial polymeric antimicrobial, polyhexamethylene guanidine (PHMG) was selected for current proof-of-concept optimization due to its excellent bactericidal capacity but moderate biocompatibility. Eosin-Y (EoS) was copolymerized to afford EoS-labeled polymer conjugates, poly(2-(dimethylamino) ethyl methacrylate-co-eosin), P(DMAEMA-co-EoS), which was conjugated with PHMG to afford a novel polymeric antimicrobial, P(DMAEMA-co-EoS)-b-PHMG-b-P(DMAEMA-co-EoS), noted as PEoS-PHMG. It could efficiently kill broad-spectrum bacteria by physical damage and photodynamic therapy. Compared with PHMG, the bacterial inhibition of PEoS-PHMG was potentiated after the functionalization. Furthermore, PEoS-PHMG exhibited low cytotoxicity and minimal hemolysis, which was demonstrated by cell viability assays toward LO2 cells and RAW 264.7 cells as well as hemolytic assays against red blood cells. These results confirmed that the resultant PEoS-PHMG could act as promising alternative antibacterial materials with excellent broad-spectrum bacterial inhibition and favorable biocompatibility.
A highly sensitive electrochemiluminescence (ECL) biosensing method was developed for monitoring casein kinase Ⅱ (CK2) at subcellular level via bio-bar-code assay. A bio-bar-code probe (h-DNA/AuNPs/pDNA) prepared by conjugating phosphorylated DNA (p-DNA) and hairpin DNA (h-DNA) onto gold nanoparticles (AuNPs) was used as a carrier for ECL signal reagent (Ru(phen)32+) while a specific peptide was used as a recognition substance. A gold ultramicroelectrode with a diameter of 400 nm was fabricated and then modified with the specific peptide via self-assembly technique to obtain peptide modified gold ultramicroelectrode. The peptide on gold ultramicroelectrode was phosphorylated in the presence of CK2 and adenosine 5'-triphosphate, and then the phosphorylated peptide was integrated with the h-DNA/AuNPs/p-DNA through a process mediated by zirconium cations (Zr4+), and finally Ru(phen)32+ was intercalated into h-DNA. A "signal on" ECL method was developed for the detection of CK2 in the range of 0.005-0.2 U/mL with a detection limit of 0.001 U/mL. Additionally, combined efficient subcellular phosphorylation in vivo with bio-bar-code-based ECL biosensing method, the ECL method was further applied to monitor CK2 at subcellular level without tedious subcellular fractionation. It was found that the concentration of CK2 by inserting the peptide modified gold ultramicroelectrode into the nucleus was higher than that into cytoplasm of HeLa cells. A distinct heterogeneity among CK2 concentrations in single cells was observed for cellular heterogeneity assessment.
In this paper, the Pt/SnO2 nanostructures were prepared via a facile one-step microwave assisted hydrothermal route. The structure of the introduced Pt/SnO2 and its gas-sensing properties toward CO were investigated. The results from the TEM test reveal that Pt grows on the SnO2 nanostructure, which was not found for bulk in this situ method, constructing Pt/SnO2. The results indicated that the sensor using 3.0 wt% Pt/SnO2 to 100 ppm carbon monoxide performed a superior sensing properties compared to 1.5 wt% and 4.5 wt% Pt/SnO2 at 225 ℃. The response time of 3.0 wt% sensor is 16 s to 100 ppm CO at 225 ℃. Such enhanced gas sensing performances could be attributed to the chemical and electrical factors. In view of chemical factors, the presence of Pt facilitates the surface reaction, which will improve the gas sensing properties. With respect to the electrical factors, the Pt/SnO2 plays roles in increasing the sensor's response due to its characteristic configuration. In addition, the one-step in situ microwave assisted process provides a promising and versatile choice for the preparation of gas sensing materials.
Noble metal is usually used to improve the gas sensing performance of metal oxide semiconductor (MOS) due to its better catalytic properties. In this work, we reported a synthesis of Pd/ZnO nanocomposite by an in situ reduction with ascorbic acid (AA). It was found that Pd/ZnO sensor has excellent selectivity to CO and the response of the Pd/ZnO sensor towards 100 ppm CO was as high as 15 (Ra/Rg), obviously higher than that of the pristine ZnO sensor (1.4) when the working temperature is 220 ℃. Moreover, the pure ZnO sensor almost has no selectivity to CO, but the Pd/ZnO sensor has excellent selectivity to CO, which may be ascribed to the electronic sensitization of Pd. Our present results demonstrate that the Pd can significantly improve the gas-sensing performance of metal oxide semiconductor and the obtained sensor has great potential in monitoring coal mine gas.
Ag- and Pt-doped WO3·0.33H2O nanorods with high response and selectivity to NH3 were synthesized from a tungsten-containing mineral of scheelite concentrate by a simple combined process, namely by a high pressure leaching method to obtain tungstate ions-containing leaching solution and followed by a hydrothermal method to prepare corresponding nanorods. The microstructure and NH3 sensing performance of the final products were investigated systematically. The microstructure characterization showed that the as-prepared WO3·0.33H2O nanorods had a hexagonal crystal structure, and Ag and Pt nanoparticles were uniformly distributed in the WO3·0.33H2O nanorods. Gas sensing measurements indicated that Ag and Pt nanoparticles not only could obviously enhance NH3 sensing properties in terms of response, selectivity as well as response/recovery time, but also could reduce the optimal operating temperature at which the highest response was achieved. The highest responses of 22.4 and 47.6 for Ag- and Pt-doped WO3·0.33H2O nanorods to 1000 ppm NH3 were obtained at 225 and 175 ℃, respectively, which were about four and eight folds higher than that of pure one at 250 ℃. The superior NH3 sensing properties are mainly ascribed to the catalytic activities of noble metals and the different work functions between noble metals and WO3·0.33H2O.
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